This project is concerned with a detailed characterization of one of the principle proteinases produce by the differentiating cellular slime mold, Dictyostelium discoideum. This enzyme (called Proteinase I) is conjugated with phosphotyl moieties. Preliminary studies have suggested that these moieties influence Proteinase I's specificity for degrading enzymes. The proposed studies are directed towards: (1) a chemical characterization of the phosphoryl moieties associated with Proteinase I, (2) an analysis of how these moieties affect the specificity of the proteinase and (3) an investigation of the mechanism of regulation Proteinase I activity during differentiation.